Rizzo leads a well-funded and important research program on oomycete and fungal diseases of forest trees and orchard crops. His program blends forest ecology and plant pathology, with projects that advance science in both arenas, while also generating information essential for development of management practices. His publications – more than 120 in diverse journals – reveal the breadth, depth, and exceptional quality of his research, providing information germane to disease management while contributing to fundamental principles of disease ecology. He is best known for his pioneering work on Phytophthora ramorum, the cause of sudden oak death (SOD), which has had a devastating impact on hardwood forests in California. Much of what is presently known about the biology of P. ramorum and the epidemiology of SOD derives from research in his lab and labs with which he is collaborating. Most of his publications since 2002 are on this pathosystem, with recent studies that include new and emerging Phytophthora species. This research also has examined SOD-fire interactions, demonstrating the potential for interacting disturbances to initiate novel successional trajectories and compromise ecosystem resilience. He has conducted over 500 media interviews, participated in documentaries for the Public Broadcasting Service, the USDA Forest Service, and University of California Cooperative extension, and given over 150 talks as part of an effort to inform the public about SOD and what they can do to prevent its spread. As the science advisor for the California Oak Mortality Task Force, Rizzo has provided steady leadership and sensible outreach to stakeholders and regulatory agencies during times of a highly charged political atmosphere arising from the public concerns of the impacts of SOD on western forests and nurseries.
Rizzo has also made significant contributions in other areas of forest ecology and health. He and his team have examined the ecological role of major pathogen/insect complexes in coniferous forest stands of the Sierra Nevada with the goal of applying the knowledge gained to management. Another important research effort was an NSF-sponsored study on mycorrhizal biodiversity and population biology in Sierra oak-grassland ecosystems. This research revealed previously undescribed mycorrhizal fungi, including several new genera. His ability to address important questions from the laboratory to landscape levels, and connect that information to forest and ecosystem health management attests to his intellect, creativity, and deep understanding of plant pathology principles.
Rizzo has made extraordinary contributions to plant pathology and mycology education. His efforts have positioned the teaching program in the Department of Plant Pathology, with its strong tradition in graduate education, to better engage and attract undergraduate students. Most notable among many accomplishments has been his establishment of the department’s first undergraduate major. The visionary nature of this effort is apparent from the high level of student interest in the new Global Disease Biology major, which has already enrolled over 270 students. He also has served as director of the collegiate Science and Society program, a general education program with courses that allow the students to discover interdisciplinary connections linking natural and social sciences with societal and cultural issues. Upon taking the helm of this program in 2004, he turned an obscure collection of courses into one the largest instructional programs on campus, serving nearly 3,000 students every year and providing new teaching opportunities for plant pathology faculty. Rizzo is one of the most active instructors in the department. The diverse list of courses that he has taught or co-taught include Introductory Mycology; Advanced Mycology; Mushrooms, Molds, and Society; The Tree of Life; Ecology of Forest Diseases; Disease Policy and Intervention; and Introduction to Global Disease Biology. The high regard students have for him is reflected in his stellar teaching evaluations. He also has mentored 20 graduate students and seven postdoctoral scientists who have gone on to have productive careers in plant pathology.
Rizzo has been recognized with a number of awards, including the APS Pacific Division Early Career Award (2002), the Distinguished Alumnus award, Plant Pathology Department, University of Minnesota (2004), the E.S. Luttrell Lecture, University of Georgia (2009), the Rosie Perez Memorial Lecture, North Carolina State University (2012), the MSA William H. Weston Teaching Award (2012), and the Western Extension Directors Association Award of Excellence (2015).
Throughout his career, Rizzo has been deeply committed to the department, university, stakeholder groups and his profession. His contributions to APS include service as an Associate Editor for Phytopathology and participation in various APS symposia. He has also led the Department of Plant Pathology to effectively meet new challenges in research, teaching, outreach, and administration, and contributed to numerous Department, College, University, statewide and national committees. His accomplishments in forest pathology, as a strong representative of the discipline to the public, as a skillful administrator, inspiring mentor, and exemplary teacher, Rizzo is most deserving of recognition as an APS Fellow.